The Geographical and Ecological Distribution of Arboreal Psocoptera

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Annu. Rev. Entomol. 1985.30:175-196. Downloaded from arjournals.annualreviews.org by Mr. Bas van Berkum on 10/10/07. For personal use only. Annual Reviews www.annualreviews.org/aronline 186 THORNTON Although New Guinea has been inadequately surveyed, there are indications that it has been an important link between the greater Sunda islands and the islands of the Outer Melanesian Arc in the case of the Pseudocaeciliidae, Peripsocidae, Ectopsocidae, a subgroup of the Myopsocidae, and Calopsocus (Calopsocidae) and Epipsocopsis (Epipsocidae) (77, 89). Considerable evolution has occurred in New Guinea itself with the production of seven endemic genera. There is also speculation that differentiation of philotarsid genera may have occurred in the area, where several unusual forms are found (77, 86). Relatively recent contributions from the New Guinea area to the faunas of northeast Australia in the above families and the Stenopsocidae, and to the fauna of east Australia in the Myopsocidae, Stenopsocidae, and Psilopsocidae are indicated. Biogeographical studies on the archipelagos of the southwestern Pacific are still incomplete, although specialist collections have been made as far as Tonga. It is already clear that no single hypothesis can explain existing patterns, which vary from family to family and within some families. Within the Philotarsidae, for example, vicaxiance and dispersal explanations have been offered for different sections of the family (81,83). The subfamily Zelandopsocinae, strictly confined to the Inner Melanesian Arc, has a species swarm on New Caledonia, and links between New Zealand and New Guinea. are recognizable. In contrast, the Outer Arc has been colonized by the sister subfamily Aaroniellinae, probably by dispersal. The Calopsocidae and Epipsocidae also occur on the Outer Arc, and in the Pseudocaeciliidae, Psocidae, Lepidopsocidae, and Myopsocidae there has been radiation in Fiji (82). The Fijian fauna (81 species) is 60% endemic, and in general an Oriental-Melanesian origin is indicated. Tonga’s fauna is an attenuation of that of Fiji. In the Psocidae also, a variety of patterns can be seen. Amphigerontiines extend only as far as Norfolk Island and New Zealand, and the genus Psococerastis does not appear to have penetrated either the Inner or Outer Melanesian Arcs. Of the Psocinae, Ptycta, the only genus of the family in Micronesia (six species), occurs in Australia, has three species in the Bismarcks, and weakly represented along the Outer Melanesian Arc as far as Tonga, but, remarkably, has not yet been found in New Guinea. Its range in this region appears to complement that of the related Copostigma, a genus that is unknown from Australia, has five species in New Guinea, is absent from the Bismarcks and Solomons, but has four species in the New Hebrides and seven in Fiji. Clematoscenea, like Copostigtna, is absent from Australia and well represented in New Guinea (eight species), but through the Melanesian Arcs their ranges are mutually exclusive. Ninety species are known from Micronesia, 54 of which occur in the southern Mafianas. Endemism is highest (over 30%) on Truk, the southern Marianas, and Palaus; Yap and Kusaie, with faunas of a size similar to that of
Annu. Rev. Entomol. 1985.30:175-196. Downloaded from arjournals.annualreviews.org by Mr. Bas van Berkum on 10/10/07. For personal use only. Annual Reviews www.annualreviews.org/aronline DISTRIBUTION OF ARBOREAL PSOCOPTERA 187 Truk, show relatively little endemism, whereas Ponape shows a moderate degree. Apparently there is no endemism in the northern Marianas, which are younger and more impoverished than the southern Marianas, nor in the Marshalls, Gilberts, or Caroline atolls, which are very low and very young. Oriental species make up about 15% of the fauna of each island group, and there are a few New Guinea species (87). In the Hawaiian archipelago there is a remarkable development of two endemic genera of elipsocids, Kilauella (ca 145 spp.) and Palistreptus (20 spp.) and the genus Ptycta (Psocidae) (51 spp.), making up over 80% of fauna. Endemicity is greatest on Kauai, the oldest and most isolated island of the group. In the case of the genus Ptycta, the "Maui complex," which is a group of four islands subjected to anastomoses and subdivisions during glacial cycles, appears to have been the site of a major burst of speciation. The endemic elipsocids have affinities with the Propsocinae of the southern hemisphere rather than the Elipsocinae. The remaining 42 species represent 20 genera of 12 families (84, 85). From the above it will be clear that we are not yet in a position to summarize definitively the biogeography of Psocoptera on a word scale. The lace curtain of hard data has all kinds of holes in it, although in a few places interesting patterns can be seen. ECOLOGICAL DISTRIBUTION Information on the distribution of arboreal psocids within geographical areas has been accumulating in recent years. In general, their occurrence appears to be related to the distribution and nature of available food on tree surfaces. Habitat ALTITUDE A reduction in diversity with increasing altitude has been demonstrated in Switzerland: only 14 of 55 species occur over 1900 m (upper subalpine zone) and all of these species occur in the lower, montane zone (1100-1500 m) (33). In the Engadine valley the richest psocid fauna was found in montane pine forest (34). Of course, vegetation type must also be considered along with temperature, moisture, and food availability (which are probably all interrelated) in determining the altitudinal distributions of psocids. Mount Kenya has relatively clear-cut altitudinal vegetative zones that are determined by changes in temperature, humidity, and rainfall. The Podocarpus zone (2440-3120 m) was found to support 28 psocid species, and 12 were confined to this zone (21). Only two species were found in the extremely wet Hagenia zone (3050-3200 m), and both occurred at lower elevations. One these was very rare; the other appears to be stenotopic and is found only
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The Geographical and Ecological Distribution of Arboreal Psocoptera

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